Filtering To Increase Effective Yields of Image Sensor

The addition of special-purpose signal-processing circuitry has been proposed to overcome some of the deleterious effects of hardware faults in integrated-circuit image sensors of active-pixel-sensor (APS) type and possibly of other types. The mathematical basis of the method is median filtering in a small neighborhood (typically of 3 × 3 or 5 × 5 pixels) centered, in turn, on each pixel; that is, one seeks to replace the intensity signal for each pixel with the median-intensity signal for its neighborhood. From the perspective of a human observer viewing the image on a remote video display, such median filtering would reduce or eliminate the visible effects of malfunctioning single pixels or of malfunctioning rows or columns of single-pixel width - the faults most commonly observed in large state-of-the-art integrated-circuit image sensors. Thus, the effective production yields of the image sensors would be enhanced.